/*
 * Copyright 2002-2015 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.context;

import org.springframework.core.ResolvableType;
import org.springframework.core.ResolvableTypeProvider;
import org.springframework.util.Assert;

/**
 * An {@link ApplicationEvent} that carries an arbitrary payload.
 *
 * <p>Mainly intended for internal use within the framework.
 *
 * @param <T> the payload type of the event
 * @author Stephane Nicoll
 * @since 4.2
 */
@SuppressWarnings("serial")
public class PayloadApplicationEvent<T> extends ApplicationEvent implements ResolvableTypeProvider {

    private final T payload;


    /**
     * Create a new PayloadApplicationEvent.
     *
     * @param source the object on which the event initially occurred (never {@code null})
     * @param payload the payload object (never {@code null})
     */
    public PayloadApplicationEvent(Object source, T payload) {
        super(source);
        Assert.notNull(payload, "Payload must not be null");
        this.payload = payload;
    }


    @Override
    public ResolvableType getResolvableType() {
        return ResolvableType.forClassWithGenerics(getClass(), ResolvableType.forInstance(getPayload()));
    }

    /**
     * Return the payload of the event.
     */
    public T getPayload() {
        return this.payload;
    }

}
